1. Field of the Invention
The present invention relates to a roll stand arrangement for rolling wire with a finishing block arranged following the last stand of the intermediate group of a wire rolling mill and composed of fixedly connected roll stands with grooved rolls, and a skin pass block arranged following and having the same configuration as the finishing block, wherein the roll stands of the skin pass block have an oval/oval groove sequence and a subsequent round groove sequence.
2. Description of the Related Art
Roll stand arrangements of this type have the purpose, in addition to achieving a relatively substantial reduction of the wire strand leaving the finishing block by means of the oval/oval groove sequence, to achieve by means of the round groove sequence a high dimensional accuracy of the wire strand leaving the skin pass block. In order to achieve this object, it had to be ensured that the fine grain structure of the rolled strand achieved with the significant reduction and the correspondingly high rolling temperature using the alternating oval/oval groove sequence of the finishing block, was maintained during the passes through the skin pass block, and that especially no grain growth which would have destroyed this fine grain structure could take place during the passes of the wire strand in the final sizing rolling phase through the round/round groove sequence with corresponding low reduction.
In order to meet this object, EP 512 735 B1 suggests a skin pass block whose groove sequence, in addition to an oval groove at the entry side, is composed of a sequence of two or more round grooves. Since the tendency of the wire strand to rotate between the round grooves cannot be counteracted by appropriate guide elements, the stands of this embodiment must be arranged very closely one behind the other; another even more important reason for this close arrangement is that a temperature drop which would negatively influence the fine grain structure achieved in the preceding rolling steps must be prevented.
In addition to the difficulties occurring in connection with the control of the rates of rotation of the roll stands with round groove rolls in order to maintain the necessary temperature with the slight reduction, the necessary close arrangement of the roll stands in the skin pass block makes it difficult to mount normal larger roll stands, as they are used, for example, in the finishing block, and also makes it difficult to mount flexible wire guide means, particularly roller guide means. The close arrangement of the roll stands results in additional difficulties if each roll stand is to be driven directly through an independent controllable individual drive. Because of the narrow space available, it is usually also not possible to exchange individual roll stands against roll stands with larger dimensions for using correspondingly larger roll diameters. Consequently, the roll stand arrangements of this type are not very flexible with respect to the controllable reductions as well as with respect to the range of wire diameters which can be rolled.